Apparatus for feeding speciments into evacuated chambers

ABSTRACT

APPARATUS FOR FEEDING SPECIMENS INTO AN EVACUATED CHAMBER COMPRISES A VACUUM LOCK HAVING A SPECIMEN CARRIER PISTON MOVABLE WITHIN A GAS-TIGHT CYLINDER BETWEEN A FIRST POSITION AT WHICH THE SPECIMEN IS INSERTED IN A SPACE IN THE CARRIER, A SECOND POSITION AT WHICH THE CARRIER SPACE IS EXPOSED TO A ROUGH VACUUM, AND A THIRD POSITION AT WHICH THE CARRIER SPACE COMMUNICATES WITH THE HIGH VACUUM OF THE CHAMBER FOR THE DISCHARGE OF THE SPECIMEN. IN COMBINATION WITH THIS VACUUM LOCK, SUCH APPARATUS CAN INCLUDE A SPECIMEN STORAGE AND TRANSFER DEVICE IN THE FORM OF A MAGAZINE INTO WHICH THE SPECIMENS ARE DEPOSITED FROM THE VACUUM LOCK AND WHICH IS ROTATABLE WITHIN A HOLLOW COMPARTMENT COMMUNICATING WITH THE SAID EVACUATED CHAMBER FOR THE TRANSFER AND DISCHARGE OF THE SPECIMEN.

L.-ASPINAL EI'AL 3,559,453

APP'ARATUSFOR FEEDING SPECIMENS INTO EVACUATED CHAMBERS Feb.2,197 1;

v 3 Sheets-Sheet 1 Filed July 17. 1968 Feb. 1971;. ME ASQ'NAL Em 3,559,453

Ai mmus FOR FEEDING SPECIMENS INTO EVACUATED CHAMBERS Filed July 17. 1959 3 Sheets-Sheet 2 Not.

Filegl July 17. 1968 3 Sheets-Sheet s Fig.3

United States Patent 3,559,453 APPARATUS FOR FEEDING SPECIMENS INTO EVACUATED CHAMBERS Michael Leslie Aspinal, Bilton, Rugby, and David Hazelby, Grandborough, Rugby, England, assignors to Associated Electrical Industries Limited, London, England, a British company Filed July 17, 1968, Ser. No. 745,609 Claims priority, application Great Britain, Apr. 19, 1967, 17,984/ 67 Int. Cl. G01n 7/14 US. C]. 73-19 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for feeding specimens into an evacuated chamber comprises a vacuum lock having a specimen carrier piston movable within a gas-tight cylinder between a first position at which the specimen is inserted in a space in the carrier, a second position at which the carrier space is exposed to a rough vacuum, and a third position at which the carrier space communicates with the high vacuum of the chamber for the discharge of the specimen. In combination with this vacuum lock, such apparatus can include a specimen storage and transfer device in the form of a magazine into which the specimens are deposited from the vacuum lock and which is rotatable within a hollow compartment communicating with the said evacuated chamber for the transfer and discharge of the specimen.

This invention relates to apparatus for feeding specimens into evacuated chambers, and one application of the invention is to apparatus for the measurement of gas contents of solids, for example, the measurement of oxygen, nitrogen, or hydrogen in, say, copper. It is to be appreciated that the use of the invention is not limited to this type of'apparatus.

In one method of measuring the gas contentin a solid, for example a metal, the gas released when a sample of the solid is melted under a vacuum is measured. By using an analysing section operating at low pressure (0.3 to 0.001 mm. Hg), the bottom limit in the measurement of oxygen in a one gram sample can be lowered to p.p.m.

It is necessary to feed into the apparatus solid metal specimens, for example in the form of one or more 4 millimetre cubes, and it is essential to be able to feed in the desired single cube, or the desired number of cubes, without any possibility of error due to feeding of the wrong number of cubes. Further, the introduction of air during the introduction of the specimens should be made as small as possible, since the apparatus cannot operate immediately accurately at high vacuum, and a considerable time may be required to return the vacuum to its original high level.

An object of the present invention is the provision.

of improved apparatus for feeding specimens into evacuated chambers, which positively limits the number of specimens fed to a desired number and which operates with the introduction of only a very small amount of unwanted air or other gas.

According to one aspect of the present invention, apparatus for feeding specimens into an evacuated chamber comprise a gas-tight housing and a specimen carrier mounted in that housing and movable between first, second and third positions only in that order, the specimen carrier being so arranged that in the first position the specimen is in communication with an ambient space from which the specimen has been inserted into the carrier, in the second position the specimen is exposed to a rough vacuum of the order of to 20 microns, and in the third position the specimen is exposed to a high vacuum in the evacuated chamber, the specimen carrier being arranged for the receipt of the specimen in the first position and for the discharge of the specimen into the evacu' ated chamber in the third position.

According to another aspect of the present invention, apparatus for feeding specimens into an evacuated chamber includes the apparatus according to the first aspect aforesaid in combination with a transfer device subjected to the high vacuum of the evacuated chamber and in the form of a rotating member which is arranged with in a hollow compartment and can be rotated from outside the evacuated chamber, the specimen carrier arranged to feed specimens one at a time to the rotating member at a first location in the transfer device and means for the discharge of specimens from the rotating member at a second location in the transfer device spaced from the first location, whereby a specimen fed to the rotating member can be moved by rotation of the member before the addition of a second specimen, and thereafter will be maintained in spaced relation from, and will be discharged separately from, the second specimen.

The invention will now be described, by way of example, with reference to the accompanying partly diagrammatic drawings, in which:

FIG. 1 is a side elevation of a furnace section of ap paratus for the measurement of the gas content of a metal specimen and of associated means for feeding metal specimen cubes to the furnace;

FIG. 2 is a sectional side elevation of the means for feeding metal specimen cubes shown in FIG. 1, but drawn to a larger scale than in that figure, and

FIG. 3 is an enlarged part sectional fragmentary side elevation of a modified form of associated means for feeding metal specimen cubes to the furnace.

Referring to FIG. 1, a furnace section 1 has its outlet duct connected through an oil diffusion pump 5 to apparatus by which the furnace section can be evacuated, and to apparatus by which gases given off in the furnace section can be analysed in a mass spectrometer to determine their quantity and their composition. That apparatus does not form part of the present invention and is recited merely as showing one use of the apparatus of the present invention.

The furnace section 1 includes a vertically extending silica furnace tube 7 closed at its lower end and clamped at its upper end to a stainless steel manifold 9. Mounted inside the furnace tube 7 is a graphite crucible 11 provided at its upper end with a graphite funnel 13. The funnel 13 serves to support the graphite crucible 1 1 inside a silica crucible 17. The space between the silica and graphite crucibles is packed with graphite powder which has passed through a mesh sieve. The top rim of the silica crucible is turned in so that there is the minimum of gap between the silica crucible and the graphite funnel. This prevents graphite powder being blown out of the crucible during evacuation or outgassing. The furnace tube 7 is sealed to the manifold 9 by means of a Viton ring 19 which can be clamped tightly to the furnace tube 7 by tightening of a ring 21.

A 3 kilowatt, 2. megacycles per second induction heating coil 23 encircles the part of the furnace tube 7 in which the crucibles are located. A top flange 25 of the manifold has fitted to it a block 27 on top of which is mounted a specimen vacuum lock 29 and through which extends an inner part of a sample storage tube 31. The vacuum lock 29 is used for the insertion of sample into the storage tube 31 without seriously affecting the vacuum in the apparatus. The samples used are in the form of one or more 4 millimetre cubes of the metal to be examined. A guide passage 33 extends downwardly into the manifold and the furnace tube and enables an operator to cause a metal sample to fall into the funnel 13 and thus into the graphite crucible 11. A viewing window 35 is provided at the upper end of the guide passage 33 and enables, through a suitable reflecting prism disposed outside the window, an optical pyrometer to be used to measure temperatures inside the crucible 11. A stopper operating arm 37 extends horizontally from the block 27 and has arranged in it an iron slug 39 connected by a fine molybdenum wire 41 to a graphite plug 43 for the funnel 13. By movement of. the slug 39 along the arm 37, using a magnet (not shown) arranged outside the arm 37, the plug 43 can be raised and lowered as desired to uncover and to block the funnel 13.

Referring also to FIG. 2, the vacuum lock 29 consists of a horizontally extending cylinder '45 in which is disposed a piston 47 carrying two O-rings 49 by which the left-hand end of the piston is sealed as regards vacuum to the cylinder wall. Near its right-hand end the piston 47 is formed with a blind radial cavity 51 which when the piston is at the right-hand limit of its travel (as shown in FIG. 2) and is properly oriented in its bore is aligned with a port 53 in the cylinder wall. Port 53 is large enough for the admission of one of the specimen cubes, and the cavity 51 is large enough to accept that cube. A plug 55 can be screwed into an outer extension of the port 53 and when in place seals that port in a fluid-tight manner. A piston rod 57 extends horizontally away from the right-hand end of the piston 47 and at the end of the cylinder 45 extends through a sealing ring 59, through a block 61 formed with a transverse bore 63 which intersects the bore which accommodates the piston rod, and through an outer sealing ring 65 between the block 61 and a clamping block 66. An outer part of the rod extends past a pinion 67 arranged to engage a rack 69 on the piston rod and, by rotation of the pinion by a knob 71 the piston 47 can be moved between its two limiting axial positions. When in its left-hand position the piston can be rotated manually through 180 degrees by rotating the housing 90 which enters the bore in the clamping block 66 and is retained by set bolt 91 which enters a groove extending half round the circumference of housing 90. The piston 47 is normally locked in position to prevent external pressure forcing the piston to the left, by a spring loaded safety catch 92 which engages teeth (not shown) in the rack 69 and which catch will be lifted clear of the rack before operating the knob 71 to drive the rack by the pinion 67.

An intermediate part of the piston rod 57 is formed with an axially extending groove 75 so arranged that when the piston is in a first position, that shown in FIG.

2, this groove lies wholly within the block 61, so arranged that when the piston is in a second position, to the left of that shown in FIG. 2, this groove connects the righthand end of the cylinder 45 to the transverse bore 63, and so arranged that when the piston is a third position, to the limit of its travel towards the left in FIG. 2, the groove lies wholly in the cylinder 45. The transverse bore 63 is connected to a source of a rough vacuum, i.e. a vacuum lying in the range to microns.

The cylinder is formed at its bottom with a port 81 so arranged that when the piston 47 is at its limiting left-hand position and has been rotated through 180 degrees, the cavity 51 is aligned with the port. Port 81 communicates with an intermediate point via a hole in the glass storage tube 31 housed within a metal tube 32. At its left-hand end the tube 31 communicates with the vertical guide passage 33, and disposed within the tube 31 is a spiral member 83 of square cross section connected at its right-hand end to a spindle 85 extending through a vacuum-tight gland 87 and carrying outside the tube 31 a knob 89 by which the spiral member 83 can be rotated so that it acts as an Archimedean screw. It will be seen that a metal specimen cube falling down through port 81 will lie between two turns of the spiral member 83, and can be moved along the tube 31 at will by rotation of the knob 89.

In use of the apparatus, the plug 55 is removed and a metal specimen cube is dropped into the cavity 51, the piston being in its first position. The plug 55 is then replaced and tightened to produce a vacuum tight seal. The piston 47 is unlocked and is moved to its second position, in which the groove 75 bridges the sealing ring 59 so that the rough vacuum in the transverse bore 63 is applied to the right-hand end of the cylinder 45, so that the port 53, and the cavity 51 are reduced to that rough vacuum of 10 to 20 microns. Further movement of the piston 47 to the left causes the groove 75 to move clear of the ring 59, so that the right-hand end of the cylinder 45 is again sealed. Upon continued movement towards the left, the piston rings 49 pass the port 81 so that the part of the cylinder 45 to the right of the rings 49 is placed in communication with the vertical guide passage 33, which is under the high vacuum used in the operation of determining the gas content of the specimen.

When the piston 47 is in its third position, it is turned through 180 degrees about its longitudinal axis and the metal sample cube falls out of the cavity down through the port 81 into the sample storage tube 31. The spiral member 83 is then rotated to move the sample cube along the storage tube and if desired a second sample cube, or further sample cubes, are similarly fed into the storage tube so as to lie between different turns of the spiral member 83. Several cubes can be stored at the same time in the tube 31 at spaced locations.

When it is desired to feed a cube into the crucible 13, the spiral member 83 is rotated through a sufficient angle by means of the knob 89 to cause the sample to fall out of the left-hand end of the tube 31 into the guide passage 33.

It will be seen that only a small quantity of air is released into the high vacuum apparatus each time a metal sample cube is inserted, and this quantity of air is at the pressure of the rough vacuum in the transverse bore 63.

The vacuum lock can be of metal construction, preferably stainless steel, with the exception of the drive mechanism and its housing. The storage tube can have a stainless steel outer shell with a glass inner sleeve. The spiral member 83 can be of glass, metal or metal coated with glass.

Referring now to FIG. 3, the vacuum lock 29 is of the same form as that already described and illustrated with reference to FIGS. 1 and 2, but in this case it is associated with a modified form of cube storage and transfer device 93 on which it is mounted.

Thus, the port 81, leading from the vacuum lock 29 communicates, via an intermediate port 82, with one of a number of holes 94 provided in a magazine disc 95 which is mounted for rotation within a circular vacuum tight chamber 96 formed between the two sealed halves of a storage/transfer block 97. The block 97 is mounted on the block 27 so that the guide passage 33 communicates with the chamber 96 and port 81 through a port 98 which is axially aligned with the diametrical pitch circle along which the holes 94 are spaced in the magazine.

There are nineteen holes equally spaced around an arc of 270, and for the sake of clarity, FIG. 3 is shown as a. developed section on central planes at right angles to each other passing through the first hole positioned in axial alignment with port 81 and through the nineteenth hole positioned in axial'alignment with the guide passage 33 and viewing window 35.

In use, a specimen cube is deposited and stored in up to eighteen of the holes 94, the nineteenth hole being kept empty to allow for inspection and for furnace temperature to be measured when the magazine 95 is fully loaded.

For feeding a specimen into the crucible 11 through the guide passage 33, the magazine can be indexed, one hole at a time, in either direction by rotating a drive knob 99 through which causes its driving pins 101 to engage notches on a dial 102 fixed on an end of the magazine shaft 103 which is vacuum sealed through the block 97. Although not shown, the notches in the dial are numbered and register against an index line for giving a visual indication of the position of the magazine so as to assist in the loading, storing and transfer operations.

We claim:

1. Apparatus for feeding specimens into an evacuated chamber comprising:

a gas-tight housing having a specimen receiving port and a specimen discharge port adapted for communication with the chamber;

a specimen carrier movably mounted in the housing;

actuable means connected to the carrier for moving it between a first position where the carrier may be charged with a specimen through the specimen receiving port, a second position, and a third position where the specimen may be discharged from the carrier through the discharge port, in that order;

and means for controlling the environmental pressure for the specimen at the first position of said carrier, and at the second position of said carrier where the specimen is exposed to a rough vacuum of the order of to microns, and at the third position of said carrier where the specimen may be exposed to a high vacuum in the evacuated chamber.

2. Apparatus according to claim 1, wherein the gastight housing is a cylinder and the specimen carrier is a piston movable within the cylinder, the piston having a radial recess for the reception of the specimen.

3. Apparatus for feeding specimens into an evacuated chamber including in combination apparatus according to claim 1 with a transfer device comprising:

a gas-tight compartment having an .inlet port communicating at a first location with said discharge port and an outlet port for communicating with the evacuated chamber at a second location spaced from the first location;

means mounted in said compartment for sequentially receiving said specimens at said inlet port, maintaining them separate from one another, moving said specimens from said inlet port while they are so maintained and sequentially releasing them at said outlet port;

whereby a specimen fed into said transfer device will be maintained in spaced relation with respect to preceding and succeeding specimens for separate releasing at said outlet port.

4. Apparatus according to claim '3, wherein said last mentioned means comprises an Archimedean screw, and the gas-tight compartment is a tubular passage, whereby the specimens are fed to and discharged from the screw at said first and second locations respectively in its axial length.

5. Apparatus according to claim 3, wherein said last mentioned means comprises a disc having a number of apertures spaced radially around an arc in the disc, and

6 the gas-tight compartment is a circular chamber, Where by the specimens are fed to and discharged from the apertures at said first and second locations respectively in their circular travel path.

6. Apparatus for feeding specimens into an evacuated chamber comprising:

a gas-tight housing having a specimen receiving port and a specimen discharge port adapted for communication with the chamber;

a specimen carrier which is movably mounted in the housing and which has a cavity for receiving a specimen;

first sealing means between the specimen carrier and the housing;

second sealing means between the specimen carrier and the housing which sealing means is disposed on the opposite side of the cavity to the first sealing means;

actuable means connected to the carrier for moving it between a first position where the cavity may be charged with a specimen through the specimen receiving port which is then sealed off from the specimen discharge port by the first sealing means, a second position in which the cavity is still sealed off from the specimen discharge port by the first sealing means, and a third position where a specimen may be discharged from the cavity through the specimen discharge port which is, in said third position, sealed off from the specimen receiving port by the second sealing means, and

a pressure controlling means to maintain a rough vacuum of the order of 10 to 20 microns in the cavity when the specimen carrier is in the second position.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 463,142 11/1968 Switzerland 7319 OTHER REFERENCES The Determination of Gases in Metals by Vacuum Fusion, J. E. Still, Report of a Symposium, The Iron and Steel Institute Special Report 68 (1960), pp. 44 to 49.

RICHARD C. QUEISSER, Primary Examiner C. E. SNEE III, Assistant Examiner 

